JP2006208126A - Battery current detector for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the detection accuracy of a current sensor for detecting charge/discharge current of a battery. <P>SOLUTION: A battery current is detected by a current sensor 17 while detecting a heater current by a heater current detection circuit 21 in synchronization with times at which a heater 20 of an air-fuel ratio sensor 18 switches itself from ON to OFF (or from OFF to ON). An amount ΔIbat of change in the battery current and an amount ΔIsen of change in the heater current are calculated to calculate a tolerance K (=ΔIbat/ΔIsen-1) with respect to a battery current detection value of this time from a ratio between the two. The tolerance K is stored in a backup RAM 22 to create a learning map on the tolerance K with battery current detection values used as a parameter. In integrating the detection values to presume the charged state of the battery 12, the learning map on the tolerance K previously stored in the backup RAM 22 is used to interpolate/correct the detection values. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery current detecting device for a vehicle having a function of detecting a charging / discharging current of a battery mounted on the vehicle.

  In recent years, as shown in Patent Document 1 (JP-A-5-322998) and Patent Document 2 (JP-A-2001-78365), a charge / discharge current of a battery mounted on a vehicle is detected by a current sensor, There is one in which the detected current value is integrated and the battery capacity is calculated based on the integrated current value. In such a battery capacity monitoring system, since the detection error of the current sensor directly leads to the detection error of the battery capacity, it is necessary to increase the detection accuracy of the current sensor in order to increase the detection accuracy of the battery capacity.

  Therefore, in Patent Document 1, the error current value (tolerance of the initial characteristics) of the current sensor is stored in advance in the memory, and the detected current value of the current sensor is corrected with the error current value.

  However, since the cause of the detection error of the current sensor is not only the tolerance of the initial characteristic but also the tolerance due to deterioration with time, the detected current value of the current sensor can be obtained only by the tolerance of the initial characteristic stored in advance as in Patent Document 1. Cannot be corrected accurately.

Therefore, in Patent Document 2, the offset tolerance of the current sensor is calculated based on the current integrated value from the previous full charge to the current full charge and the integration period, and the detected current value of the current sensor is offset corrected. Like that.
JP-A-5-322998 (first page, etc.) JP 2001-78365 A (first page, etc.)

  In addition to the above-mentioned initial characteristic tolerance, tolerance due to deterioration over time, and offset tolerance, there are linearity tolerances (tolerances of slopes of detection characteristic lines of current sensors). Even if the correction method of No. 1 and Patent Document 2 are combined, the tolerance of linearity cannot be corrected, and the correction accuracy of the current value of the current sensor cannot be sufficiently increased.

  The present invention has been made in view of such circumstances. Accordingly, an object of the present invention is to provide a vehicle battery current detection device that can improve the accuracy of correction of the detection value of the battery current detection means.

  In order to achieve the above object, the invention according to claim 1 detects a battery current detecting means for detecting a charge / discharge current of a battery mounted on the vehicle, and a current flowing through any one of the electric loads mounted on the vehicle. In a vehicle having a load current detection means for performing correction, the correction means corrects the detection value of the battery current detection means based on the relationship between the detection value of the battery current detection means and the detection value of the load current detection means. It is a thing. Since electric current is supplied from the battery to the electric load mounted on the vehicle, there is a relationship that if the current flowing through the electric load increases, the discharge current of the battery increases correspondingly. Therefore, it is related to the relationship between the detection value of the battery current detection means and the detection value of the load current detection means (for example, the relationship between the change in the detection value of the battery current detection means and the change in the detection value of the load current detection means). Therefore, if this relationship is determined, the detection value of the battery current detection means can be accurately corrected based on the determination result.

  In this case, as in claim 2, the relationship between the detected value of the battery current detecting means and the detected value of the load current detecting means is determined for a plurality of battery currents having different magnitudes, and the detected value of the battery current detecting means is determined. It is better to correct it. Thus, if the relationship between the detection value of the battery current detection means and the detection value of the load current detection means is determined for a plurality of battery currents of different sizes, the linearity tolerance (detection characteristic line of the detection characteristic line) of the battery current detection means is determined. (Tolerance of inclination) can be determined with high accuracy, and the correction accuracy of the detection value of the battery current detection means can be further increased.

  According to a third aspect of the present invention, the relationship between the detection value of the battery current detection means and the detection value of the load current detection means is determined by energizing the electric load that is the detection target of the load current while the operation of the internal combustion engine is stopped. You may do it. In other words, since the energization to almost all electric loads of the vehicle is turned off while the operation of the internal combustion engine is stopped, the battery current is detected by energizing only the electric load that is the load current detection target during the operation stop of the internal combustion engine. If the relationship between the detected value of the means and the detected value of the load current detecting means is determined, the relationship between the detected value of the battery current detecting means and the detected value of the load current detecting means can be obtained without being affected by other electric loads. Further, the determination can be made with high accuracy, and the correction accuracy of the detection value of the battery current detection means can be further increased.

  According to a fourth aspect of the present invention, there is provided an abnormality determination means for determining that either the battery current detection means or the load current detection means is abnormal when the correction amount by the correction means exceeds a predetermined range. Also good. In short, if either the battery current detection means or the load current detection means becomes abnormal, the correction amount by the correction means becomes abnormally large. Therefore, if the correction amount by the correction means becomes an abnormal value, the battery current detection means It becomes possible to determine that either of the load current detection means is abnormal.

  Further, as in claim 5, based on the relationship between the detected value of the battery current detecting means and the detected value of the load current detecting means, it is determined whether either the battery current detecting means or the load current detecting means is abnormal. It may be determined. For example, in the case where no relationship is recognized between the behavior of the detection value of the battery current detection means and the behavior of the detection value of the load current detection means, either the battery current detection means or the load current detection means Can be determined to be abnormal.

  Hereinafter, three Examples 1 to 3 embodying the best mode for carrying out the present invention will be described.

  A first embodiment of the present invention will be described with reference to FIGS. First, the configuration of the entire system will be described with reference to FIG.

  The control device 11 is supplied with power from the battery 12 via the key switch 13, controls the operation of the ignition device 14 and the injection device 15 during engine operation, and based on the integrated value of the charge / discharge current of the battery 12. The charging state of the battery 12 is estimated and the control current of the generator 16 is controlled to control the charging state of the battery 12 near the target value.

  The control device 11 includes various sensors such as a current sensor 17 (battery current detection means) for detecting a charge / discharge current (hereinafter referred to as “battery current”) of the battery 12 and an air-fuel ratio sensor 18 for detecting an air-fuel ratio of exhaust gas. Sensors are connected. The air-fuel ratio sensor 18 includes a sensor element 19 that generates a limit current that is substantially proportional to the air-fuel ratio of the exhaust gas, and a heater 20 (electric load) that heats and activates the sensor element 19. Is detected by a heater current detection circuit 21 (load current detection means) provided in the control device 11. The heater current detection circuit 21 can detect the current value with higher accuracy than the current sensor 17 that detects the battery current.

  The control device 11 is provided with a backup RAM 22 as a rewritable nonvolatile memory in addition to a ROM for storing various programs and data such as maps, and a RAM for temporarily storing calculation data, sensor data, and the like. It has been. The backup RAM 22 stores data (for example, a tolerance K learning map, an engine control learning value, abnormality diagnosis information, etc., which will be described later) that needs to be retained during the OFF period of the key switch 13. In addition, power is supplied from the battery 12 to various on-vehicle electric devices (electric loads).

  Further, the control device 11 calculates the tolerance K (correction amount) based on the relationship between the detection value of the current sensor 17 (battery current detection value) and the detection value of the heater current detection circuit 21 (heater current detection value). It functions as correction means for correcting the detection value of the current sensor 17. Hereinafter, a method of correcting the detection value of the current sensor 17 will be described with reference to the time chart of FIG.

  When the engine is started, energization of the heater 20 of the air-fuel ratio sensor 18 is started, and heating of the sensor element 19 of the air-fuel ratio sensor 18 is started. Thereafter, the battery current is detected by the current sensor 17 at a predetermined sampling period, and the heater current is detected by the heater current detection circuit 21 at a predetermined sampling period. Then, after the temperature of the sensor element 19 of the air-fuel ratio sensor 18 reaches the activation temperature, the sensor element 19 is alternately switched on (on) / off (off) according to the temperature of the sensor element 19, thereby The temperature of 19 is controlled to the active temperature range.

Then, the battery current detection values Ibat (i), Ibat (i-1) and the heater current detection value Isen () detected at timings (i−1) and (i1) immediately before and after switching the heater 20 from ON to OFF, respectively. Based on i-1) and Isen (i), the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i) when the heater 20 is switched off are calculated.
ΔIbat (i) = Ibat (i−1) −Ibat (i)
ΔIsen (i) = Isen (i−1) −Isen (i)

After that, from the ratio of the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i), the tolerance K (i) (correction amount) of the current battery current detection value Ibat (i) is calculated by the following equation. To do.
K (i) = ΔIbat (i) / ΔIsen (i) −1
Here, when ΔIbat (i) = ΔIsen (i), the tolerance = 0.

  In the first embodiment, in synchronism with the timing (i) at which the heater 20 is turned off, the tolerance K (i) in the battery current detection value Ibat (i) at that time (i) is calculated by the above equation. A tolerance K is calculated for each of a plurality of detected battery current values Ibat of different sizes, and is stored in the backup RAM 22 as a learned value of the tolerance K. Thereby, a learning map (Ibat, K) of tolerance K using the battery current detection value Ibat as a parameter is created, and the learning value of the tolerance K is sequentially updated, so that the tolerance K can be changed over time.

  When the battery current detection value Ibat is integrated to estimate the state of charge (battery capacity) of the battery 12, the battery current detection value Ibat is calculated using the learning map of the tolerance K stored in the backup RAM 22. Thus, the interpolation correction is performed, and the corrected battery current detection value Ibat is integrated.

For example, when the current battery current detection value Ibat is Ia, the tolerances K (Ib) and K (Ic) of the two points (Ib and Ic) closest to the current battery current detection value Ia from the learning map of the tolerance K are shown. And a tolerance K (Ia) in the current battery current detection value Ia is calculated by the following equation.
K (Ia) = {K (Ib) -K (Ic)} * (Ia-Ic) / (Ib-Ic)

Thereafter, using this tolerance K (Ia), the current battery current detection value Ia is corrected by the following equation.
Battery current detection value after correction = Ia + (Ia−Ic) × K (Ia)
As a result, various tolerances including the linearity tolerance of the battery current detection value Ia (tolerance of initial characteristics, tolerance due to deterioration with time, offset tolerance) are collectively corrected.

  The above-described calculation of the tolerance K (i) is executed by the control device 11 at a predetermined cycle (for example, 5 ms cycle) by the tolerance calculation routine of FIG. When this routine is started, first, in step 101, the current battery current detection value Ibat (i) detected by the current sensor 17 is read. In the next step 102, the current heater current detected by the heater current detection circuit 21 is read. The detection value Isen (i) is read.

  Thereafter, the timing at which the heater 20 of the air-fuel ratio sensor 18 switches from ON to OFF is detected by the processing of Step 103 and Step 104, and the current battery current detection value Ibat (i) is processed by the processing of Steps 105 to 107 at that timing. ) To calculate the tolerance K (i).

  This process will be described in detail. First, in step 103, it is determined whether or not the heater 20 of the air-fuel ratio sensor 18 is ON. If the heater 20 is ON, this routine is performed without performing the subsequent processes. When the heater 20 is turned off, the process proceeds to step 104 to determine whether the heater 20 was turned on at the previous activation of this routine. If “No” is determined in step 104, that is, if the heater 20 is determined to be OFF both in the previous time and this time, it is determined that it is not the calculation timing of the tolerance K (i) (OFF switching timing of the heater 20). Thus, this routine is terminated without performing the subsequent processing.

If “Yes” is determined in step 104, that is, if the heater 20 is previously turned on and is currently turned off, it is determined that the calculation timing of the tolerance K (i) (the heater 20 OFF switching timing) is reached. Then, the process proceeds to step 105, where the heater current change amount ΔIsen (i), which is the difference between the previous heater current detection value Isen (i-1) and the current heater current detection value Isen (i), is calculated.
ΔIsen (i) = Isen (i−1) −Isen (i)

Thereafter, the process proceeds to step 106, where a battery current change amount ΔIbat (i) that is a difference between the previous battery current detection value Ibat (i−1) and the current battery current detection value Ibat (i) is calculated.
ΔIbat (i) = Ibat (i−1) −Ibat (i)

Thereafter, the routine proceeds to step 107, and the tolerance K (i) in the current battery current detection value Ibat (i) is calculated from the ratio of the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i) by the following equation. calculate.
K (i) = ΔIbat (i) / ΔIsen (i) −1

  The tolerance K (i) calculated as described above is stored in the backup RAM 22, and a learning map (Ibat, K) of the tolerance K using the battery current detection value Ibat as a parameter is created.

  In the first embodiment described above, the tolerance K (i) in the current battery current detection value Ibat (i) is calculated from the ratio between the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i). Thus, the learning map of the tolerance K using the battery current detection value Ibat as a parameter is created. Therefore, various tolerances (initial values including the linearity tolerance of the battery current detection value Ibat are used by using the learning map of the tolerance K. (Characteristic tolerance, tolerance due to deterioration with time, offset tolerance) can be collectively corrected, and the correction accuracy of the battery current detection value Ibat can be improved. Thereby, the charge state (battery capacity) of the battery 12 can be accurately estimated from the integrated value of the corrected battery current detection value Ibat.

  In the first embodiment, the tolerance K is calculated in synchronization with the timing at which the heater 20 of the air-fuel ratio sensor 18 switches from ON to OFF. On the contrary, the heater 20 of the air-fuel ratio sensor 18 is calculated. The tolerance K may be calculated in synchronism with the timing when is switched from OFF to ON.

  In the first embodiment, the tolerance K is calculated while the engine is operating (while the key switch 13 is ON). However, during the engine operation, many other in-vehicle electric devices other than the heater 20 are used. Since the battery is energized, the battery current change amount ΔIbat (i) may include the influence of the current change of the in-vehicle electrical device other than the heater 20, which causes the accuracy of calculation of the tolerance K to be reduced.

  Therefore, in the second embodiment of the present invention shown in FIGS. 4 and 5, the engine is considered in consideration that the power supply to almost all on-vehicle electric devices is turned off while the engine is stopped (while the key switch 13 is OFF). During the stop, the heater 20 of the air-fuel ratio sensor 18 is energized to calculate the tolerance K.

  In the second embodiment, as shown in FIG. 4, the air-fuel ratio sensor after a predetermined time elapses after the engine is stopped (after the key switch 13 is turned off) until almost all the on-vehicle electric devices are turned off. 18 heaters 20 are temporarily turned ON / OFF, and the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen () are synchronized with the timing at which the heater 20 switches from ON to OFF (or from OFF to ON). The tolerance K is calculated by calculating i).

  In the second embodiment, the control device 11 executes the heater energization control routine during engine stop in FIG. 5 at a predetermined cycle (for example, 5 ms cycle) while the engine is stopped (while the key switch 13 is OFF). ON / OFF of the heater 20 is controlled as follows. First, in step 201, it is determined whether or not the key switch 13 is turned off. If it is not turned off, this routine is terminated without performing the subsequent processing.

  On the other hand, if the key switch 13 is turned off, “Yes” is determined in the above step 201 and the process proceeds to step 202 to determine whether or not the tolerance K has been calculated during the current engine stop. If the calculation has been completed, this routine is terminated without performing the subsequent processing.

  If it is determined in step 202 that the tolerance K has not been calculated, the process proceeds to step 203, where the engine stop is performed by adding the start cycle (5 ms) of this routine to the previous count value Tcnt (I-1) of the soak timer. The subsequent elapsed time Tcnt (I) is measured. Thereafter, the routine proceeds to step 204, where it is determined whether or not the elapsed time Tcnt after the engine is stopped is within a range from a predetermined heater ON switching timing KON to a heater OFF switching timing KOFF (KON ≦ Tcnt <KOFF). If "Yes" is determined, the process proceeds to step 208, the heater ON flag xoxht is set to 1, and the heater 20 is turned on (or maintained in the ON state).

  On the other hand, when the elapsed time Tcnt after engine stop is not within the range from the predetermined heater ON switching timing KON to the heater OFF switching timing KOFF (when Tcnt <KON or Tcnt ≧ KOFF), step 204 to step 205 Then, the heater ON flag xoxht is reset to 0 and the heater 20 is turned OFF (or the OFF state is maintained). Thereafter, the process proceeds to step 206, where it is determined whether or not Tcnt ≧ KOFF. If it is determined as “No”, this routine is terminated. If it is determined as “Yes”, the process proceeds to step 207. The count value Tcnt of the soak timer is reset to the initial value (0).

  By performing the processing as described above, the heater 20 is turned on when the elapsed time Tcnt after the engine is stopped is within a predetermined range from the heater ON switching timing KON to the heater OFF switching timing KOFF. The battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i) are calculated in synchronization with the timing when the heater 20 is switched from ON to OFF (or from OFF to ON) while the engine is stopped, and the tolerance K is calculated. Is calculated. Other matters are the same as those in the first embodiment.

  In the second embodiment described above, the heater 20 of the air-fuel ratio sensor 18 is temporarily turned ON / OFF while the engine is stopped, and is synchronized with the timing when the heater 20 is switched from ON to OFF (or from OFF to ON). Since the tolerance K is calculated by calculating the battery current change amount ΔIbat (i) and the heater current change amount ΔIsen (i), the tolerance K can be accurately determined without being affected by the on-vehicle electrical equipment other than the heater 20. It can be calculated well, and the correction accuracy of the battery current detection value Ibat can be improved.

  Note that the method for calculating the tolerance K is not limited to the above-described embodiments. For example, during a period in which the heater 20 is temporarily turned on while the engine is stopped, the heater current is increased or decreased, and a plurality of different heater currents are determined for the battery. The tolerance K may be calculated by obtaining the relationship between the detected current value Ibat and the detected heater current value Isen. Of course, the heater current during the ON period of the heater 20 may be fixed to a constant value, and the tolerance K may be calculated from the relationship between the battery current detection value Ibat and the heater current detection value Isen. At this time, it is preferable to subtract the current consumption of the electric load (for example, the control device 11) other than the heater 20 from the battery current detection value Ibat.

  In addition, if there is an electric load with a current detection function other than the heater 20 of the air-fuel ratio sensor 18, the tolerance K is calculated from the relationship between the current detection value of the electric load and the battery current detection value. May be.

  In the third embodiment of the present invention shown in FIG. 6, the abnormality diagnosis routine of FIG. 6 is executed at a predetermined cycle using the tolerance K (correction amount) calculated by the same method as in the first or second embodiment. Thus, the function as the abnormality determination means in the claims is realized. When this routine is started, first, at step 301, it is determined whether or not the tolerance K has been calculated. If it has not been calculated, this routine ends. If it has been calculated, the routine proceeds to step 302. Then, it is determined whether or not the tolerance K is within a predetermined range. As a result, if the tolerance K is within the predetermined range, it is determined that both the current sensor 17 and the heater current detection circuit 21 are functioning normally. If the tolerance K is not within the predetermined range, It is determined that one of the heater current detection circuits 21 is abnormal (step 303).

  In short, if either the current sensor 17 or the heater current detection circuit 21 becomes abnormal, the tolerance K becomes abnormally large. If the tolerance K becomes an abnormal value, whichever of the current sensor 17 or the heater current detection circuit 21 is used? Can be determined to be abnormal.

  Note that it may be determined whether either the current sensor 17 or the heater current detection circuit 21 is abnormal based on the relationship between the detection value of the current sensor 17 and the detection value of the heater current detection circuit 21. . For example, when there is no relationship between the behavior of the detection value of the current sensor 17 and the behavior of the detection value of the heater current detection circuit 21, whichever of the current sensor 17 and the heater current detection circuit 21 is used. Can be determined to be abnormal.

1 is a block diagram schematically showing the overall configuration of a system according to a first embodiment of the present invention. 3 is a time chart for explaining a control example of the first embodiment. 6 is a flowchart illustrating a process flow of a tolerance calculation routine according to the first embodiment. 6 is a time chart for explaining a control example of the second embodiment. 7 is a flowchart illustrating a process flow of a heater energization control routine during engine stop according to a second embodiment. 10 is a flowchart showing a flow of processing of an abnormality diagnosis routine of Example 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Control apparatus (correction means, abnormality determination means), 12 ... Battery, 13 ... Key switch, 17 ... Current sensor (battery current detection means), 18 ... Air-fuel ratio sensor, 19 ... Sensor element, 20 ... Heater (electric load) ), 21 ... heater current detection circuit (load current detection means), 22 ... backup RAM

Claims (5)

Battery current detection means for detecting a charge / discharge current (hereinafter referred to as “battery current”) of a battery mounted on the vehicle, and load current detection means for detecting a current flowing in any of the electric loads mounted on the vehicle. In the vehicle
A battery current detection for a vehicle, comprising: a correction means for correcting the detection value of the battery current detection means based on a relationship between a detection value of the battery current detection means and a detection value of the load current detection means. apparatus.   The correction means determines the relationship between the detection value of the battery current detection means and the detection value of the load current detection means for a plurality of battery currents having different sizes, and corrects the detection value of the battery current detection means. The battery current detection device for a vehicle according to claim 1.   The correction means determines the relationship between the detection value of the battery current detection means and the detection value of the load current detection means by energizing the electric load while the operation of the internal combustion engine is stopped. Or the battery current detection apparatus of the vehicle of 2.   2. The apparatus according to claim 1, further comprising an abnormality determination unit that determines that either the battery current detection unit or the load current detection unit is abnormal when a correction amount by the correction unit exceeds a predetermined range. The battery current detection device for a vehicle according to any one of claims 1 to 3. In a vehicle comprising battery current detection means for detecting a charge / discharge current of a battery mounted on the vehicle, and load current detection means for detecting a current flowing through any of the electric loads mounted on the vehicle,
An abnormality determination unit that determines whether one of the battery current detection unit or the load current detection unit is abnormal based on a relationship between a detection value of the battery current detection unit and a detection value of the load current detection unit. A battery current detection device for a vehicle, comprising:

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